1. Field of the Invention
This invention relates generally to semiconductor devices and more specifically to a high power semiconductor laser diode package that provides efficient collimation of a laser diode bar to conserve source brightness for far-field applications.
2. Related Art
High-power laser diode bar packages are commonplace on the laser market. Diode bars consisting of 10-100 individual light-emitting sources produce output power in the tens of watts under continuous-wave operation. Yet a difficulty still remains in effectively collecting and collimating the light emitted from these high power laser diode arrays. A major contribution to this difficulty is the inherent asymmetry of the laser diode output beam.
An exemplary laser diode bar is shown schematically in FIG. 1. Laser diode bar 102 may include approximately 20-30 individual light-emitting sources 104 arranged along array axis 106. A typical light-emitting source, such as source 104a, has a lateral dimension 108 (along array axis 106), which can range from approximately 20 to 500 micrometers (.mu.m). In the transverse direction (perpendicular to the array axis 106), however, the light-emitting source has a transverse dimension 110 of approximately 1 to 2 .mu.m. The divergence in the lateral direction, also referred to as the slow-axis divergence, is characterized by a lateral divergence angle in the range of approximately 8.degree. to 20.degree.. The divergence in the transverse direction, also referred to as the fast-axis divergence, is much stronger, with a typical transverse divergence angle ranging from approximately 20.degree. to 100.degree.. In order to provide a laser source with a greater range of uses, optical systems comprising lenses, spherical optics, mirrors, and waveguides have been proposed to reduce the inherent asymmetry of the output beam profile. Preferably, these optical systems can reduce the inherent asymmetry, while still conserving individual source brightness. See, e.g., U.S. Pat. No. 5,168,401, issued Dec. 1, 1992 to Endriz (incorporated by reference herein in its entirety).
However, other considerations such as laser package size and/or thermal management of these high-power devices can present a laser designer with a tradeoff that results in less-than-optimal optical output beam divergences. Thus, what is needed is a high power laser diode package that provides for optimal coupling of the laser diode output beam.